Beyond Sexual Dimorphism and Habitat Boundaries: Coloration Correlates with Morphology, Age, and Locomotor Performance in a Toad

Coloration is often key in animal communication, and is frequently subjected to strong natural and sexual selection, often with opposed directions: natural selection typically favors cryptic colorations whereas sexual selection may favor conspicuous colorations. Also, different coloration traits may convey different pieces of information. Plus, coloration may vary among habitats, mirroring local selective pressures. In this work, we test if color parameters (luminosity, chroma, and hue) of back and throat are related to different life-history and morphological traits in Epidalea calamita toads. Furthermore, we check possible variability of color parameters between agrosystem and natural habitat toads. Toad coloration was sexually dimorphic, which suggests a role of coloration in sexual communication. Moreover, coloration correlated with age, body size, hindlimb length, and sprint speed. These findings suggest communication based on coloration beyond sex recognition: coloration could act as a signal of overall quality of bearers, with a potential role in mate choice. Moreover, coloration differed between habitats. Greener backs in agrosystem toads could indicate greater intensity of predator pressure, while their higher saturation could indicate greater investment in mate attraction. This result is aligned with previous findings that agrosystem toads respond to reduced lifespan with greater reproductive investment.Toads were captured in accordance with permissions from Junta de Andalucía issued to the authors (reference AWG/ MGD/MGM/CB). The authors assumed the expenses of the work. FJZ-C was partly supported by a Fundación Ramón Areces postdoctoral grant and a Juan de la Cierva-Formación contract by the Spanish Government, and MC was supported by a Severo Ochoa contract (ref: SVP-2014-068620)